System for measurement of volume of flow of a flowable granular-like material

ABSTRACT

A system for measurement of volume of flow of a flowable grannular-like material such as grain in a partially confining flow path, which system includes a vane positioned to be deflected by the material at a point in the flow path where it becomes virtually free of said confinement, the position of said vane establishing an analogue electrical signal which is converted to digital for read out.

United States Patent [1 1 Diehl Nov. 27, 1973 SYSTEM FOR MEASUREMENT OF3,351,236 11/1967 Sorenson et a]. 222 55 x VOLUME OF FLOW OF A FLOWABLEGRANULAR-LIKE MATERIAL John A. Diehl, Arlington, Va.

Assignee: Richard H. Hayes, Talmadge,

Ohio; a part interest Inventor:

[22} Filed: Oct. 19, 1972 I [21] Appl. No: 299,078

[52] U.S. Cl. 73/194 R, 73/228 [51] Int. Cl. G01f 1/00 [58] Field ofSearch 73/228, 194 R, 198; 222/55, 59; 33/121 [56] References CitedUNITED STATES PATENTS 2,033,306 3/1936 Schofield 73/228 2,552,569 5/1951McNamara 73/194 FOREIGN PATENTS OR APPLICATIONS 1,184,977 1/1965 GermanyPrimary ExaminerRichard C. Queisser Assistant Examiner.lohn P. BeauchampAtt0rneyWilliam A. Smith, Jr. et a1.

[5 7 ABSTRACT A system for measurement of volume of flow of a flowablegranular-like material such as grain in a partially confining flow path,which system includes a vane positioned to be deflected by the materialat a point in the flow path where it becomes virtually free of saidconfinement, the position of said vane establishing an analogueelectrical signal which is converted to digital for read out.

9 Claims, 5 Drawing Figures P-ATENIED Rm 2 1 ma SHEET 16F 2 Fig. 3

SYSTEM FOR MEASUREMENT OF VOLUME F FLOW OF A FLOWABLE GRANULAR-LIKEMATERIAL BACKGROUND Prior Art The use of deflectable vanes (orequivalent) for the purpose of determining volume of flow of a conveyedsubstance is well known, as evidenced by Keeler U.S. Pat. No. 2,312,216and Hillyar-Russ et al. U.S. Pat. No. 3,295,213, and such a deflectablevane has been coupled to an analogue to digital converter (German Pat.No. 1,184,977). In each of the foregoing disclosures, the deflectableelement is positioned over a movable conveying element (i.e., an endlessbelt) whereby the depth of the material on the belt (and hence thedegree of deflection) varies with factors other than the true volume ordensity of the material, notably (1) the conditions of original loadingof the belt, such as impact of free drop, force of head of material inthe case of hopper feed, and (2) conditions during transit such ascompaction by restricting elements (doctor blade, structural elements,etc.), settling due to vibration during conveyance, etc. Furthermore,the use of deflectable elements over such conveyors is limited to asubstantially horizontal flow at least to the extent that the materialwill not roll back or slide under the deflectable element as a result offactors which unpredictably affect the depth of the material, such asdiffering characteristics of adhesiveness, weight, particle shape,coarseness or fineness, etc.

Deflectable vanes have also been disclosed as creating electricalanalogue signals proportionate to the depth of material flowing in aninclined gravity type conveyor, or chute, the analogue signals beingconverted to digital for readout purposes. Such a disclosure may befound in Sorenson et al. U.S. Pat. No. 3,351,236, in which the inventorrecognizes that therate of flow along the chute 27 is a function of anumber of variables, such as the angle of the chute, the initialvelocity of the material entering the chute, the shape of the bottom ofthe chute, the form of flow restricting elements, etc. While Sorensonmentions that a simple farm type of weighing device apparatus willrequire only one transducer because of the uniform nature of materialsto be measured, namely grains, his disclosure is limited to an apparatuswherein, even with only one transducer, response is not only to the rateand amount of material flowing in the chute 27, but additionally to thevariable inclination of the flow chute, which inclination is defined asthe actual or geometrical angle of the chute. Hence, the apparatus ofSorenson operates with a dependance on a measurable inclination relativeto a standard, presumably the horizontal, and is thus limited to astatic system wherein the standard is invariable.

PURPOSES OF INVENTION In contradistinction to the aforementionedsystems,

the present invention provides a simple systemfor measurement of flow ofa flowable granularlike material which is equally well adapted to use ina static or mobile environment. In the latter the only availablereference base. While numerous additional purposes and advantages may beevident from a consideration of the ensuing specification, the followingare enumerated as representative of the principal objects of thisinvention, which are to provide 1. an accurate measurement device of lowpower requirements,

2. a measurement device requiring a minimum of moving parts,

3. a measurement device of simple and economical make up,

4. a measurement device tolerant of variations in the inclination of theflow conduit of the material undergoing flow measurement,

5. a method implementing the above objectives.

SUMMARY OF INVENTION In keeping with the foregoing objects, thisinvention involves a deflectable vane which is critically positioned ata point in theflow path of the flowable granular-like material whereatthe material undergoes a transition from the forced flow to a gravityflow. At this particular point, the material has been found to berelatively free of disturbing influences inherent in the nature of theconveying element. inclination thereof, and variations in adherance,particle size, rate or impact of initial feed. etc. This point liesbetween the termination of a positive or force feed conveying elementand a point of free flow discharge from the conveying conduit and ishereinafter referred to as a threshold point in the flow path. In thepreferred embodiment, the deflectable vane is positioned at a thresholdpoint where the depth of material crests in its transition from forcedfeed to free flow and at which it retains to a significant extent adepth determined by the volumetric characteristics of the flow, while atthe same time is released of extraneous influences of the conveyingelement or back pressure of material downstream of the measuring elementas determined by characteristics such as length and inclination of thedownstream conduit.

Moreover, and also in furtherance of the foregoing objects, thisinvention provides an electronic analogue to digital converter wherebythe deflection of the vane is integrated with time and a digital readoutis provided by solid state circuitry. The system involves a minimum ofmoving parts and power consuming elements. To this end, a counter, whichmay be either an all solid state counter or a solenoid driven impulsecounter, is driven by a circuit controlled by a pulse generatorincluding a unijunction transistor and an RC charging circuit. Ananalogue value in the form of a steady state voltage the amplitude ofwhich is derived from the position of the deflectable vane is applied tothe RC circuit in a manner that the capacitor charges at a ratedependent upon that value. When the charge reaches a predeterminedthreshold value, the unijunction transistor conducts to discharge thecondensor, thus generating a pulse to advance the counter and resettingthe RC circuit to enable it to repeat the cycle. The recurrencefrequency of pulse generation, and thus the counting rate, is dependentupon the RC charging rate and thus is an indication of the degree ofdeflection of the vane.

IDENTIFICATION OF DRAWINGS For a better understanding of the invention,reference is made to the following description taken in connection withthe accompanying drawings, in which FIG. 1 is an elevational side viewof the terminal end of a conveyor including the sensor of thisinvention,

FIG. 2 is an elevational end view of the same,

FIG. 3 is a schematic diagram of the electronic circuit of thisinvention,

FIG. 4 is a longitudinal section of the terminal end of a conveyorincluding the sensor of this invention, and

FIG. 5 is a cross section taken at V-V of FIG. 4.

DESCRIPTION OF SENSOR Referring to the drawings, and particularly toFIGS. 1 and 2, the terminal portion of a conveying element including thesensing device of this invention is generally indicated at 15. In theparticular embodiment used for illustrative purposes, the conveyorcomprises a cylindrical tube 16 and screw 21, and is capped by atransition section 17 which supports a discharge hood 18 of rectangularcross section and including a depending discharge chute 19 leading to afree discharge end 20. The particular angle of the discharge chute isnot critical except to the extent that it offers virtually no resistanceto gravity flow of materials through it. In FIGS. 1 and 2 gravity flowcommences at the junction of the bottom surfaces 14 and 13, referred toas a threshold 12.

A deflectable vane assembly generally indicated at 22 comprises a shaft23 extending through the hood 18 at a point near the upper surfacethereof and rotatably supported by appropriate bearings. A collar 24adjustably attached to said shaft carries a torque rod 25 extending in adirection normal to the shaft 23. A weight 26 is adjustably attached ata selected point near the outer extremity of the torque rod 25. Rigidlyattached to the shaft 23 inside of the hood 18 is a vane 27 alsoextending in a direction normal to shaft 23 and including a portionwhich overlies the threshold 12. While this portion could be the edge ofthe vane 27, it is preferred that the vane extend beyond the threshold12 so that a side surface thereof rests against the material beingmeasured. One end of shaft 23 is connected to an element of an angularlyadjustable shaft coupling 28, the other element of which is coupled topotentiometer 39, the housing of which is rigidly supported as bybracket 29. This arrangement permits adjustment of the vane positionrelative to the potentiometer arm to adapt to a particular installation.

Another embodiment, illustrated in FIGS. 4 and 5, is similar to that ofFIGS. 1 and 2 and hence is shown with the same reference numerals and aprime suffix. In the interest of brevity, the description of FIGS. 1 and2 is applicable here and will not be repeated. Note, however, that theembodiment of FIGS. 4 and 5 comprise a horizontally disposed force feedconveyor 16' and a vertical discharge chute 19'. Again, the dispositionand length of the chute 19 is not critical to any extent other than thatit presents no restriction to free gravity flow of the material beyondthe threshold 12'. It is commonplace on a grain combine to extend thischute by a flexible boot (not shown) into the receiving receptacle toavoid the loss of grain by its being picked up by wind.

OPERATION OF SENSOR As can be seen from an examination of FIG. 4, thedepth of the material within the force feed portion 16' of the materialvaries considerably because of the action of the conveying elements,whether they be the convoluted flights of the screw 21 as in thisexample or the flights of other known types of positive conveyors.Another factor influencing this depth involves back pressure of thematerial itself which in turn is a function of the condition of thematerial, speed of conveyance, and angle of inclination of the conveyor.The last factor is of particular importance in the case of mobileinstallations, but also must be considered in stationary installationswhere the inclination is often varied in order to hold the discharge endproximate to the top of the previously delivered material.

On the other hand, it is difficult to measure the flow during freegravity flow, most such attempts having forced resort to sophisticatedweighing systems which have proven to be excessively temperamental inmany environments.

I have found that the aforesaid difficulties can be avoided bycritically locating the sensor in a position where the vane 27 overliesthe threshold 12 where the transition from forced feed to free flow takeplace. At this point the material is still partially confined in thelateral dimensions of the path of flow, but is free of the confinementof back pressure. To this end, the pivot point of the vane 27', namelythe shaft 23 is situated upstream of the threshold 12' and the vane 27'is dimensioned and positioned so as to include a material contactingportion overlying the threshold. Thus, contact is made with the materialat a point free of influences of back pressure and where the deflectionof the vane is representative of the volume of flow and substantiallyindependent of the factors such as inclination of the apparatus.

DESCRIPTION AND OPERATION OF ELECTRONIC CIRCUITRY Referring to FIG. 3,there is disclosed the circuitry for integrating an analogue valuederived from the vane position and producing a digital signal to operatea conventional impulse counter (not shown). The impulse counter, whichmay be of the type disclosed in US. Pat. No. 1,480,738 issued Jan. l5,1924 to C. H. Veeder, is driven by a solenoid 30, the operatingpotential for which is derived from a direct current power supply hererepresented by battery 31, in series with OFF/ON switch 32 andtransistor 33. A pilot light 34 serves as an indicator that power isapplied to the system. Transistor 33 is biased to normally nonconductingcondition, and is pulsed to drive solenoid 30 by a control circuit nowto be described. Surges generated by the solenoid coil back EMF at theend of each pulse are bypassed by diode 35 in conventional fashion toavoid damage to transistor 33.

The control circuit also derives its voltage from power supply 31, butrequires a regulated voltage supply. To this end, lead 36 is providedwith a voltage dropping resistor 37, and a zener diode 38 maintains thepotential at lead 36 at a prescribed voltage which, in the preferredembodiment, is 10 volts.

In order to calibrate the analogue voltage produced at the movable tapof vane potentiometer 39, a rate adjust rheostat 40 is provided tofurther drop the regulated voltage derived from lead 36. The rate adjustpotentiometer permits counter response to be adjusted to derive aparticular volumetric measure (e.g., 1 count equal 0.1 bushel of grain)as determined by the physical parameters of the particular installation.

The position of the movable arm of potentiometer 39 is determined by theposition of the vane 27, increased deflection of the vane by increasedgrain flow volume serving to move the arm upwardly and increase thepositive voltage potential thereat. This potential appears, throughresistor 41 at the base of transistor 42, which is connected incommon-emitter circuit configuration to function as an amplifier. Anincrease in potential at the base of transistor 42 thus serves toincrease conduction therethrough and hence through resistors 43, 44 andthe emitter base circuit of transistor 45. The potential at the base oftransistor 45 thus raises to increase flow therethrough. Transistor 45is incorporated in a common-collector circuit including output resistor46 which provides an impedance match to RC timing circuit comprisingresistors 47, 48 and condensor 49 and, with resistor 50 andpotentiometer 51 comprises a voltage divider to establish an adjustablebias to control the firing level of the pulse generator, now to bedescribed.

Unijunction transistor 52 has its emitter/base 1 circuit connected inshunt with capacitor 49, operating voltage being established from itsbase 2 through current limiting resistor 53. The voltage at the base ofUJT 52 is established by adjustment of potentiometer 51 to a pointwhere, during conditions of non-conduction of transistor 45, the emitterdiode of UJT 52 is reversebiased, thus no current flows from emitter tobase 1. The function of integrating the value of the voltage appearingat the movable arm of potentiometer 39 is here accomplished by thegeneration of pulses at a rate directly proportional to the amplitude ofthat voltage, thus converting the signal from analogue to digital. Tothis end the amplified signal appears at the output of the commoncollector circuit including transistor 45 and is applied throughresistors 47 and 48 to charge capacitor 49, the value of thesecomponents establishing a charging rate dependent upon the said outputvoltage. As the voltage at the emitter of UJT 52 (Le, at the RCjunction) increases to a point where the emitter diode thereof is nolonger reverse-biased, the UJT conducts, exhibiting the negativeresistance characteristic inherent in this element, and dischargescapacitor 49 through its emitter/base 1 junction to ground lead 55. Thesudden discharge of capacitor 49 passes a negative pulse throughcapacitor 56 to the base of transistor 54. At the same time, thedischarge of capacitor 49 brings the emitter of UJT 52 back to areverse-biased condition, terminating conduction therein, and initiatinganother charging cycle in RC circuit 47, 48, 49. Inasmuch as thecharging rate is dependent on the voltage at the collector of transistor45, the pulsing cycle is repeated at a pulse rate dependent upon theanalogue voltage determined by the setting of vane potentiometer 39. TheUJT is chosen for this function because of its inherent stabletriggering threshold and high pulse current carrying (negativeresistance) capacity.

Prior to reception of the pulse through capacitor 56 transistor 54 isbiased to a normally conducting state by its base resistor 57. As apulse is received, transistor 54 cuts off, and current flow through itscollector resistor 58 is diverted through resistor 59 to the base oftransistor 33, to bring that transistor to saturation and advance pulsecounter drive solenoid 30.

The operation of the counter is conventional, and provides a numericalreadout indicative of the flow rate expressed in volume per time unit.By appropriate adjustment of vane potentiometer a calibration can bereached to provide a read out expressed as cumulative weight.

SUMMARY As is evident from a consideration of the foregoing discussion,this invention provides a simple, but critically positioned deflectablevane sensor which avoids the necessity of correlating the singlevariable quantity (material depth) with other variable and unpredictablefactors, and combines with this sensor a simple, all electronic analogueto digital electronic measuring circuit. The foregoing combination isparticularly adapted to the demanding conditions encountered in grainhandling where contamination by dust results in malfunction of movingparts which are here held to a minimum.

While preferred embodiments have been shown and described, the inventionis not limited to these embodiments, the scope thereof being properlydetermined by the following claims.

I claim:

saidvane having a free end portion extending into said flow path in agenerally downstream direction and including a portion for contactingsaid material at a point overlying said threshold.

2. The system of claim 1 wherein said free end portion terminatesdownstream of said threshold.

3. The system of claim 1 further including electrical analogue signalgenerating means operatively coupled to said deflectable vane, and anelectronic analogue to digital converting means having an inputelectrically coupled to said analogue signal generating means and anoutput at which is presented as a digital signal comprising a series ofpulses the repetition rate of which is a derivitive of said analoguesignal.

4. The system of claim 3 further including a counter and means to applysaid output pulses to said counter to obtain a numerical read out.

5. The system of claim 4 wherein said counter is incrementally driven bya solenoid driver, said driver being pulsed by said output pulses toincrementally advance said counter.

6. The system of claim 3 wherein said analogue to digital convertorcomprises a unijunction transistor including an emitter diode junction,said input being coupled to an RC circuit the capacitor of which is inshunt with said emitter diode junction.

7. The system of claim 3 wherein said derivative is a ratio of saidanalogue signal amplitude to time and said analogue signal generatingmeans includes means to adjust said amplitude and thus to vary saidratio whereby said system can be calibrated in terms of a known weightper volume of material.

8. The system of claim 3 wherein said operative coupling comprises anangular-ily adjustable shaft coupling.

9. A method of measuring the flow volume of a flowable granular-likematerial comprising the steps of e. integrating said sensed depth withtime to provide a measurement of flow rate.

1. A system for measurement of flow rate of a pulverized material movingin a flow path including a positive drive portion, a gravity flowportion, and a threshold between said portions, said system including adeflectable vane mounted for pivotal movement about an axis situatedover said path at a point upstream of said threshold, said vane having afree end portion extending into said flow path in a generally downstreamdirection and including a portion for contacting said material at apoint overlying said threshold.
 2. The system of claim 1 wherein saidfree end portion terminates downstream of said threshold.
 3. The systemof claim 1 further including electrical analogue signal generating meansoperatively coupled to said deflectable vane, and an electronic analogueto digital converting means having an input electrically coupled to saidanalogue signal generating means and an output at which is presented asa digital signal comprising a series of pulses the repetition rate ofwhich is a derivitive of said analogue signal.
 4. The system of claim 3further including a counter and meanS to apply said output pulses tosaid counter to obtain a numerical read out.
 5. The system of claim 4wherein said counter is incrementally driven by a solenoid driver, saiddriver being pulsed by said output pulses to incrementally advance saidcounter.
 6. The system of claim 3 wherein said analogue to digitalconvertor comprises a unijunction transistor including an emitter diodejunction, said input being coupled to an RC circuit the capacitor ofwhich is in shunt with said emitter diode junction.
 7. The system ofclaim 3 wherein said derivative is a ratio of said analogue signalamplitude to time and said analogue signal generating means includesmeans to adjust said amplitude and thus to vary said ratio whereby saidsystem can be calibrated in terms of a known weight per volume ofmaterial.
 8. The system of claim 3 wherein said operative couplingcomprises an angularily adjustable shaft coupling.
 9. A method ofmeasuring the flow rate of a pulverized material comprising the steps ofa. providing a predetermined flow path including, in sequence, apositive drive portion, a threshold, and a gravity flow section, b.applying a driving force to the material to impart movement theretothrough said positive drive portion and across said threshold, c.permitting free flow of said material through said gravity flow sectionwhereby said material crests in depth above said threshold, d. sensingthe depth of said material at said crest, and e. integrating said senseddepth with time to provide a measurement of flow rate.